Generally, a heating cylinder composing an injection device of an injection molding machine is provided with a plurality of heating units on the outer circumferential surface thereof along an axial direction in order to keep resin material supplied to inside the heating cylinder in a molten state, thereby the resin material is heated to a high temperature condition of around 300 [° C.] and also temperature control is performed with respect to each heating area so that the optimal temperature distribution in the axial direction is obtained. Accordingly, a heating cylinder cover covering the circumference of the heating cylinder is provided for the purpose of ensuring the heat-retaining property to enhance the energy saving and preventing an operator from coming in contact with the heating cylinder.
Conventionally, as this kind of heating cylinder covers, a heating cylinder heat retaining device disclosed in JP-No. 2004-291545, a heating cylinder protective cover disclosed in JP-No. 2013-226816, a heat retaining method disclosed in JP-No. 2010-083090, and a temperature control mechanism disclosed in JP-No. 2009-172957 are known.
The heating cylinder heat retaining device in patent literature 1 is intended to reduce the power consumption of a plastic molding machine and enhance the heat retaining effect; specifically, the surface of a heat retaining cover having a double structure using stainless material is finished to a mirror surface, thereby heat rays (electromagnetic waves) radiated from the surface of a heating cylinder are reflected toward the heating cylinder, and the heat rays (the electromagnetic waves) radiated to the opposite side of the heating cylinder by an inner reflector are reflected to the side of the heating cylinder by an outer reflector, and also, an air space doubles as a heat retaining material, which keeps the efficient heat retaining state.
The heating cylinder protective cover disclosed in patent literature 2 is intended to increase the ability of heat dissipation from the surface of the cover to the outside air, thereby keeping the surface temperature of the cover low; specifically, there are provided a resin injection mechanical section fitted with a heating cylinder with a nozzle, a fixed platen to which, out of molds that molten resin heated and melted in the heating cylinder is injected into a cavity thereof, a fixed-side mold is attached, and the heating cylinder protective cover that covers the outer circumference of the heating cylinder for heating and melting material loaded from a resin supply port, and at least part of the outer surface of the heating cylinder protective cover is coated with heat dissipating paint.
The heat retaining method disclosed in patent literature 3 is intended to mold high-quality molded products by controlling the temperature of an injection cylinder with a higher degree of accuracy than that in a case of wrapping the outer circumferential surface of an injection cylinder in a heat-insulating cover and to make the molding work more efficient by enabling a heat-retaining jacket to be easily attached to and removed from the injection cylinder; specifically, the outer circumferential surface of the injection cylinder except a nozzle touch part is entirely wrapped in the heat-retaining jacket containing heat-insulating material through a gap with a required width, thereby each site of the injection cylinder is kept at a predetermined set temperature.
The temperature control mechanism disclosed in patent literature 4 is intended to be able to easily suppress the overshoot while obtaining the energy-saving effect by using heat-insulating material; specifically, there are provided a heating cylinder that is heated by a heater to melt resin inside thereof and discharges the molten resin, a heat-insulating material that covers at least part of the circumferentially whole circumference of the heating cylinder where the heat is installed, and the temperature control mechanism that detaches at least part of the heat-insulating material from the heating cylinder according to the temperature of the heating cylinder.